[No Title Available]

Abstract

A new inseminating fish species of the family Characidae, Bryconadenos tanaothoros, from tributaries of the upper rio Xingu and upper rio Tapajós basins, Mato Grosso, Brazil is described as the type species of a new genus. This new species and the genus are characterized by a glandular organ on the anterior region of the anal fin of sexually mature males, curved lower jaw teeth, and an inseminating reproductive mode. This new genus is hypothesized as most closely related to Attonitus, a genus with three inseminating species from Peru. Bryconadenos and Attonitus are suggested as related to certain inseminating, but undescribed characid species of uncertain relationships that are similar in certain respects to species of the glandulocaudine Planaltina and to the inseminating species of Knodus. These and a few other inseminating characids are included in a previous tentative characid subgroup designated as Clade A. No species among a relatively small sample of the many species of the Clade A genus Bryconamericus were found inseminating, except Bryconamericus pectinatus. However, newly collected specimens of B. pectinatus were found to have caudal-fin squamation like that of the species of Knodus and this species is here tentatively referred to Knodus. Our investigations indicate that at least several species of Knodus, including the type species, Knodus meridae, are not inseminating, but we found two inseminating apparently new characid species that currently would be referred to Knodus. These species lack the derived anal-fin rays present in the males of K. pectinatus. Other Clade A taxa known to be inseminating, such as two species of the large genus Creagrutus, three species of Monotocheirodon (two undescribed), and the species and genera of the characid subfamily Glandulocaudinae are briefly discussed regarding possible relationships to Attonitus and Bryconadenos. The anatomical aspects of the primary and secondary sexual characteristics of Bryconadenos and Attonitus are discussed in relation to certain other inseminating characids, such as the species of Brittanichthys and Hollandichthys, that are not currently hypothesized to belong to Clade A and presumably acquired insemination independently. It is concluded that much additional data regarding the reproductive modes as well as other anatomical/physiological systems of characids currently included in and excluded from Clade A are necessary before a reasonably supported phylogeny of Clade A characids and their possible outgroup relatives can be advanced.The anal-fin gland cells of sexually active male Bryconadenos specimens are histologically indistinguishable from club cells (also called alarm substance cells) found within the skin of cypriniforms, characiforms, catfishes, and other otophysan fishes. These cells occur at the skin's surface of the anal-fin gland in male Bryconadenos where they are organized into an organ. Many other adult male characids have club cells at the anal-fin's skin surface, often associated with anal-fin hooks, but were not found or...

On a remarkable sexual dimorphic trait in the Characiformes related to the olfactory organ and description of a new miniature species of Tyttobrycon Géry (Characiformes: Characidae)

“…[4,27,70–72]). It is likely that the pheromones produced by club cells play an important role during cohort and spawning [72], and many studies have demonstrated that the olfactory epithelium is very sensitive in detecting such chemical secretions [73–77]. Therefore, the detection of male pheromone and/or other chemical secretions by other males may be the trigger for competition between these individuals.…”

Phylogenetic relationships of a new genus and species of stevardiine fish (Characiformes: Characidae: Stevardiinae) from the Río Amazonas basin, Peru

“…with Diapoma as the only exception (Thomaz et al, 2015;Vanegas-Ríos, Azpelicueta, & Malabarba, 2018). However, and as found in different phylogenetic studies using morphological data, the mere presence of the hypertrophied caudal-fin squamation does not support a monophyletic group (Ferreira, Menezes, & Quagio-Grassioto, 2011;Menezes & Weitzman, 2009;Mirande, 2018;Vanegas-Ríos, 2018;Weitzman et al, 2005).…”

“…Previous morphological classifications of the genera having modified squamation on the lower caudal-fin lobe (Menezes & Weitzman, 2009;Weitzman & Malabarba, 1998;Weitzman et al, 2005) have been substantially changed or almost completely refuted in light of either molecular data (Oliveira et al, 2011;Thomaz et al, 2015), large morphological matrices using different regions of body (Mirande, 2010;Vanegas-Ríos, 2018), or combined data sets (Mirande, 2018). However, the phylogenetic potential of the variations derived and associated with the different types of hypertrophied caudal-fin squamation can still be better interpreted, when the involved homologies are more adequately treated in cladistics terms, its contribution on the phylogenetic results is greater, as it was the case of the monophyly of Stevardiini (Vanegas-Ríos, 2018).…”

Molecular phylogeny and biogeographic history of the Neotropical tribe Glandulocaudini (Characiformes: Characidae: Stevardiinae)

“…The systematics of Glandulocaudini is historically confuse and only after restriction of the group to Lophiobrycon, Glandulocauda, and Mimagoniates by Weitzman et al (2005), it was possible to discuss more clearly the phylogenetic relationships among its species (Menezes, Weitzman, 2009). In that paper, Menezes, Weitzman provided the most recent phylogenetic hypothesis for Glandulocaudini as currently recognized, including all known species and based mostly on analyses of primary and especially secondary sexual characters of males.…”